Photodegradation of polychlorinated biphenyl congeners using simulated sunlight and diethylamine

Photodegradation of polychlorinated biphenyls (PCBs) can be an important natural decomposition mechanism. As most PCB congeners do not strongly absorb wavelength above 300 nm, sensitizers are used in the transfer of light energy to the PCB molecule in order to enhance their degradation. The objectives of this study were to determine the rate-order of reaction and the photodegradation rates of PCB congeners by simulated sunlight in the presence of diethylamine. Five PCB congeners (66, 101, 110, 118, and 138) with diethylamine were exposed to simulated sunlight from 0, 1, 2, 4, 8, to 24 hr. These five congeners constitute 45.45 % of all the Aroclor 1254 congeners. Half-lives of these congeners, after exposure to simulated sunlight and diethylamine, ranged from 3.4 to 9.9 hr. The photodegradation rate constant of the PCB congeners varied from 0.07±0.01 to 0.20±0.04 hr−1. The photodegradation rate was proportional to the concentration of the PCB congener suggesting a pseudo first order reaction of PCB photodegradation. The data also indicated that the photodegradation is independent of the concentration of diethylamine. Degradation of congener 101 was 5 times faster with simulated than with natural sunlight. The product quantum yield of PCB congeners ranged from 2.6±0.3 to 7.5±0.2 × 10−4 in the presence of diethylamine.